Asparagus Pizza with Lemon, Prosciutto, and Ricotta

Arrange the oven racks so that your top rack is about ten inches from the broiler.
Preheat the oven on the broiler setting.
Very thinly slice the asparagus spears, skipping the last 2-3 inches of the more fibrous ends. Slice the flower ends in half vertically. Zest one lemon to yield 1½ teaspoons of zest.
In a medium bowl, combine the ricotta, Parmesan, lemon zest, and pepper. Mix until smooth and well blended. Taste for salt and season if needed, keeping in mind the salty prosciutto will be topping the pizza.
Place the parbaked pizza crust or flatbread bottom side up on the sheet pan. Broil for 2-3 minutes, until the bottom is crisp and toasted
Remove the sheet pan from the oven and flip the pizza crust or flatbread so that the top is exposed.
Spread the ricotta mixture over the top of the pizza, getting right to the edges. Peel the thin layers of prosciutto from the package, tear them in half, and loosely bundle them over the top of the ricotta. Sprinkle the asparagus over the pizza and top it with the mozzarella.
Broil the pizza for 5-6 minutes, until the cheese is browned, the prosciutto starts to crisp, and the asparagus gets a bit of color. Check the pizza often as it cooks, all broilers are different and cooking times will vary.
Remove from the oven and slice into pieces. Serve immediately.